Merge pull request #1174 from storytold/fix/1111-bend-blend-spine

#1111: a blend's spine bends into a curve

crates/engine/src/cmd/draw2.rs

@@ -825,20 +825,9 @@ fn reshape_segment(s: &mut Session, p: &Value) -> Result<Value> {
     s.edit("Reshape", |d, _| {
         let path = path_mut(d, id)?;
         let sp = path.subpaths.get_mut(si).ok_or_else(|| EngineError::Other("no such subpath".into()))?;
-        if seg >= sp.segment_count() {
+        if !sp.bend_segment(seg, t, dv) {
             return Err(EngineError::Other("no such segment".into()));
         }
-        let n = sp.anchors.len();
-        // Moving both inner control points by v moves B(t) by 3t(1-t)·v. A smooth anchor stays
-        // smooth: its other handle turns with the moved one.
-        let v = dv / (3.0 * t * (1.0 - t));
-        let (i0, i1) = (seg % n, (seg + 1) % n);
-        if let Some(a) = sp.anchors.get_mut(i0) {
-            a.set_handle(true, a.h_out + v, false);
-        }
-        if let Some(b) = sp.anchors.get_mut(i1) {
-            b.set_handle(false, b.h_in + v, false);
-        }
         Ok(())
     })?;
     ok()

crates/engine/src/cmd/live.rs

@@ -14,7 +14,7 @@ use vectorcraft_doc::live::{
     PreserveShape, Spine,
 };
 use vectorcraft_doc::{Appearance, Document, Node, NodeId, NodeKind, Selection};
-use vectorcraft_geom::{Affine, PathData, Point};
+use vectorcraft_geom::{Affine, PathData, Point, Vec2};
 
 use super::edit::selected_roots;
 use super::expand::gradient_sampler;
@@ -95,6 +95,15 @@ pub fn specs() -> Vec<CommandSpec> {
             has_doc,
             spine_move_anchor
         ),
+        cmd!(
+            "object.blend.spine.reshapeSegment",
+            "Reshape Spine Segment",
+            [],
+            None,
+            "{id? (default: the selected blend), segment: index, t: 0..1, dx, dy} bend a segment of the blend's spine so its point at t moves by (dx, dy), as path.reshapeSegment bends a path's: a straight spine turns into a curve (#1111)",
+            has_doc,
+            spine_reshape_segment
+        ),
         cmd!(
             "object.blend.spine.addAnchor",
             "Add Spine Point",
@@ -640,6 +649,18 @@ fn spine_move_anchor(s: &mut Session, p: &Value) -> Result<Value> {
     ok()
 }
 
+fn spine_reshape_segment(s: &mut Session, p: &Value) -> Result<Value> {
+    const C: &str = "object.blend.spine.reshapeSegment";
+    let seg = index_param(p, "segment", C)?;
+    let t = f64_or(p, "t", 0.5).clamp(0.05, 0.95);
+    let dv = Vec2::new(f64_or(p, "dx", 0.0), f64_or(p, "dy", 0.0));
+    if !(t.is_finite() && dv.x.is_finite() && dv.y.is_finite() && dv.hypot() < 1e9) {
+        return Err(bad(C, "t, dx and dy must be finite"));
+    }
+    edit_spine(s, p, C, "Reshape Spine", |sp, _, _| if sp.bend_segment(seg, t, dv) { Ok(()) } else { Err(bad(C, "no such spine segment")) })?;
+    ok()
+}
+
 fn spine_add_anchor(s: &mut Session, p: &Value) -> Result<Value> {
     const C: &str = "object.blend.spine.addAnchor";
     let q = finite_point(p, C)?;

crates/engine/src/tests_blendspine.rs

@@ -187,3 +187,20 @@ fn key_anchors_round_trip() {
     let old: BlendSpec = serde_json::from_value(json!({"spine": {"subpaths": []}})).unwrap();
     assert!(old.key_anchors.is_empty());
 }
+
+/// #1111: a straight spine's segment bends into a curve, its middle moving where it's dragged, and
+/// the steps follow it; junk segments and deltas are refused.
+#[test]
+fn a_straight_spine_segment_bends_into_a_curve() {
+    let mut s = session();
+    let (_, _, g) = blend(&mut s);
+    s.execute("object.blend.spine.reshapeSegment", &json!({"segment": 0, "t": 0.5, "dx": 0, "dy": 40})).unwrap();
+    let spine = spec(&s, g).spine.unwrap();
+    let seg = spine.subpaths[0].segment(0);
+    use vectorcraft_geom::kurbo::ParamCurve;
+    assert!(seg.eval(0.5).distance(Point::new(55.0, 45.0)) < 1e-9, "{seg:?}");
+    assert!(center(&steps(&s, g)[1]).y > 20.0, "the step follows the curve");
+    for bad in [json!({"segment": 1, "dy": 10}), json!({"segment": 0, "dx": f64::MAX, "dy": f64::MAX}), json!({"segment": -1})] {
+        assert!(s.execute("object.blend.spine.reshapeSegment", &bad).is_err(), "{bad}");
+    }
+}

crates/engine/tests/command_sweep.rs

@@ -367,6 +367,7 @@ fn structured_junk() {
         ("object.blend.options", json!({"spacing": "distance", "value": -1e308, "orientation": 5})),
         ("object.blend.spine.moveAnchor", json!({"id": 2, "anchor": u64::MAX, "x": 1e308, "y": -1e308, "handle": "sideways"})),
         ("object.blend.spine.addAnchor", json!({"id": u64::MAX, "x": 0, "y": 0})),
+        ("object.blend.spine.reshapeSegment", json!({"id": 2, "segment": u64::MAX, "t": f64::NAN, "dx": 1e308, "dy": -1e308})),
         ("object.blend.spine.removeAnchor", json!({"anchor": -1})),
         ("object.puppetWarp", json!({"rest": true, "pins": [], "moved": []})),
         ("object.puppetWarp", json!({"rest": true, "pins": [[1e308, 0]], "moved": [[0, 0]], "expand": -5})),

crates/geom/src/path.rs

@@ -252,6 +252,24 @@ impl SubPath {
             _ => a,
         }
     }
+    /// Bend segment `seg` so its point at `t` moves by `dv`: both inner control points move by
+    /// dv / 3t(1-t), since B(t) moves by 3t(1-t) times that. A smooth anchor stays smooth: its other
+    /// handle turns with the moved one. False when there is no such segment.
+    pub fn bend_segment(&mut self, seg: usize, t: f64, dv: kurbo::Vec2) -> bool {
+        let n = self.anchors.len();
+        if seg >= self.segment_count() || n == 0 {
+            return false;
+        }
+        let v = dv / (3.0 * t * (1.0 - t));
+        if let Some(a) = self.anchors.get_mut(seg % n) {
+            a.set_handle(true, a.h_out + v, false);
+        }
+        if let Some(b) = self.anchors.get_mut((seg + 1) % n) {
+            b.set_handle(false, b.h_in + v, false);
+        }
+        true
+    }
+
     /// Split segment `seg` at parameter `t`, inserting a new anchor. Returns the new anchor index.
     pub fn insert_anchor(&mut self, seg: usize, t: f64) -> usize {
         let n = self.anchors.len();

crates/tools/src/direct.rs

@@ -90,6 +90,15 @@ enum State {
         start: Point,
         began: bool,
     },
+    /// Dragging a curved segment of a selected blend's spine: it follows the pointer
+    /// (`object.blend.spine.reshapeSegment`, #1111).
+    SpineSegment {
+        id: NodeId,
+        seg: usize,
+        t: f64,
+        start: Point,
+        began: bool,
+    },
     /// Dragging a handle of the clicked spine point.
     SpineHandle {
         id: NodeId,
@@ -170,6 +179,15 @@ fn hit_spine_point(cx: &ToolContext, p: Point, tol: f64) -> Option<(NodeId, usiz
     })
 }
 
+/// The segment of a selected blend's spine passing within `tol` of `p`: (blend, segment, t, whether
+/// it is straight).
+pub(crate) fn hit_spine_segment(cx: &ToolContext, p: Point, tol: f64) -> Option<(NodeId, usize, f64, bool)> {
+    spines(cx).into_iter().filter(|(id, _)| cx.selection.contains(*id)).find_map(|(id, path)| {
+        let (si, seg, t, _, dist) = path.nearest(p)?;
+        (dist <= tol).then(|| (id, seg, t, path.subpaths.get(si).is_some_and(|sp| sp.segment_is_line(seg))))
+    })
+}
+
 /// The spine point `sel` and whether `p` is on its outgoing handle's end (`Some(true)`) or its
 /// incoming one's.
 fn hit_spine_handle(cx: &ToolContext, sel: (NodeId, usize), p: Point, tol: f64) -> Option<bool> {
@@ -402,6 +420,11 @@ impl Tool for DirectSelectionTool {
                 if let Some((id, anchors)) = hit_frame_edge(cx, p, tol) {
                     return self.press_type_area(cx, id, anchors, p, ev.mods.shift);
                 }
+                // A curved segment of a selected blend's spine reshapes, as a path's does.
+                if let Some((id, seg, t, false)) = hit_spine_segment(cx, p, tol) {
+                    self.state = State::SpineSegment { id, seg, t, start: p, began: false };
+                    return vec![];
+                }
                 if let Some(out) = self.guide.press(cx, ev) {
                     self.state = State::Idle;
                     return out;
@@ -546,6 +569,22 @@ impl Tool for DirectSelectionTool {
                 out.push(Action::Preview("object.blend.spine.moveAnchor".into(), json!({"id": id.0, "anchor": anchor, "x": q.x, "y": q.y})));
                 out
             }
+            (PointerKind::Drag, State::SpineSegment { id, seg, t, start, began }) => {
+                let mut out = vec![];
+                if !began {
+                    if p.distance(start) < cx.tol(3.0) {
+                        return out;
+                    }
+                    out.push(Action::Begin("Reshape Spine".into()));
+                    self.state = State::SpineSegment { id, seg, t, start, began: true };
+                }
+                let d = p - start;
+                out.push(Action::Preview(
+                    "object.blend.spine.reshapeSegment".into(),
+                    json!({"id": id.0, "segment": seg, "t": t, "dx": d.x, "dy": d.y}),
+                ));
+                out
+            }
             (PointerKind::Drag, State::SpineHandle { id, anchor, out }) => vec![Action::Preview(
                 "object.blend.spine.moveAnchor".into(),
                 json!({"id": id.0, "anchor": anchor, "handle": if out {"out"} else {"in"}, "x": p.x, "y": p.y, "independent": ev.mods.alt}),
@@ -583,6 +622,7 @@ impl Tool for DirectSelectionTool {
                 | State::MoveObject { began, .. }
                 | State::Segment { began, .. }
                 | State::SpinePoint { began, .. }
+                | State::SpineSegment { began, .. }
                 | State::TypeArea { began, .. },
             ) => {
                 self.state = State::Idle;
@@ -814,6 +854,45 @@ mod tests {
         assert!(t.overlays(&cx).iter().any(|o| matches!(o, Overlay::Anchor { filled: true, .. })), "the clicked point shows");
     }
 
+    /// #1111: the Anchor Point tool bends a selected blend's straight spine; Direct Selection
+    /// reshapes a curved spine segment and leaves a straight one alone, as it does a path's.
+    #[test]
+    fn spine_segments_bend_with_the_anchor_point_tool_and_direct_selection() {
+        let (mut d, g, _) = blend_doc();
+        let mut s = Selection::default();
+        s.set([g]);
+        let p = paint();
+        let drag = |t: &mut dyn crate::Tool, cx: &ToolContext| {
+            t.pointer(cx, &PointerEvent::new(PointerKind::Down, 160.0, 311.0));
+            let a = t.pointer(cx, &PointerEvent::new(PointerKind::Drag, 160.0, 351.0));
+            t.pointer(cx, &PointerEvent::new(PointerKind::Up, 160.0, 351.0));
+            a
+        };
+        let straight = cx(&d, &s, &p);
+        let a = drag(crate::create("anchorPoint").as_mut(), &straight);
+        assert!(
+            matches!(a.last(), Some(Action::Preview(c, v)) if c == "object.blend.spine.reshapeSegment" && v["id"] == g.0 && v["segment"] == 0 && v["dy"] == 40.0),
+            "{a:?}"
+        );
+        let a = drag(&mut DirectSelectionTool::new(false), &straight);
+        assert!(!a.iter().any(|x| matches!(x, Action::Preview(c, _) if c == "object.blend.spine.reshapeSegment")), "straight: {a:?}");
+        // The spine bent upward: Direct Selection takes it from where it passes.
+        let mut sp = vectorcraft_geom::SubPath::polyline(&[Point::new(110.0, 310.0), Point::new(210.0, 310.0)], false);
+        sp.bend_segment(0, 0.5, vectorcraft_geom::Vec2::new(0.0, 20.0));
+        let Some(NodeKind::Blend { spec, .. }) = d.node_mut(g).map(|n| &mut n.kind) else { panic!("blend") };
+        (spec.spine, spec.key_anchors) = (Some(PathData::single(sp)), vec![0, 1]);
+        let mut t = DirectSelectionTool::new(false);
+        let curved = cx(&d, &s, &p);
+        t.pointer(&curved, &PointerEvent::new(PointerKind::Down, 160.0, 330.0));
+        let a = t.pointer(&curved, &PointerEvent::new(PointerKind::Drag, 160.0, 345.0));
+        assert_eq!(a[0], Action::Begin("Reshape Spine".into()));
+        assert!(
+            matches!(&a[1], Action::Preview(c, v) if c == "object.blend.spine.reshapeSegment" && v["segment"] == 0 && v["dx"] == 0.0 && v["dy"] == 15.0),
+            "{a:?}"
+        );
+        assert_eq!(t.pointer(&curved, &PointerEvent::new(PointerKind::Up, 160.0, 345.0)), vec![Action::Commit]);
+    }
+
     #[test]
     fn direct_and_group_selection_pick_blend_keys() {
         let (d, g, k1) = blend_doc();

crates/tools/src/draw2/anchor.rs

@@ -4,7 +4,7 @@
 //! Delete: click an anchor to remove it, re-fitting the neighbouring curve (Alt = add).
 //! Anchor Point: click a smooth anchor → corner; drag an anchor → pull out smooth handles; drag a
 //! handle → move it independently (Shift: at 45° steps round its anchor); drag a segment → reshape
-//! the curve.
+//! the curve, a selected blend's spine's too, straight or curved (#1111).
 //! Scissors: click a path to split it there.
 
 use serde_json::json;
@@ -19,9 +19,30 @@ use crate::{Action, Cursor, Mods, Overlay, PointerEvent, PointerKind, Tool, Tool
 #[derive(Clone, Copy, Debug)]
 enum State {
     Idle,
-    Convert { id: NodeId, si: usize, ai: usize, start: Point, began: bool },
-    Handle { id: NodeId, si: usize, ai: usize, out: bool, began: bool },
-    Reshape { id: NodeId, si: usize, seg: usize, t: f64, start: Point, began: bool },
+    Convert {
+        id: NodeId,
+        si: usize,
+        ai: usize,
+        start: Point,
+        began: bool,
+    },
+    Handle {
+        id: NodeId,
+        si: usize,
+        ai: usize,
+        out: bool,
+        began: bool,
+    },
+    /// Bending a segment: a path's, or (`spine`) a selected blend's spine's.
+    Reshape {
+        id: NodeId,
+        si: usize,
+        seg: usize,
+        t: f64,
+        start: Point,
+        began: bool,
+        spine: bool,
+    },
 }
 
 pub struct AnchorTool {
@@ -94,7 +115,9 @@ impl Tool for AnchorTool {
                 } else if let Some((id, si, ai)) = hit_anchor(cx, p, point) {
                     self.state = State::Convert { id, si, ai, start: p, began: false };
                 } else if let Some((id, si, seg, t)) = hit_segment(cx, p, tol) {
-                    self.state = State::Reshape { id, si, seg, t, start: p, began: false };
+                    self.state = State::Reshape { id, si, seg, t, start: p, began: false, spine: false };
+                } else if let Some((id, seg, t, _)) = crate::direct::hit_spine_segment(cx, p, tol) {
+                    self.state = State::Reshape { id, si: 0, seg, t, start: p, began: false, spine: true };
                 }
                 vec![]
             }
@@ -128,6 +151,10 @@ impl Tool for AnchorTool {
                             json!({"id": id.0, "subpath": si, "anchor": ai, "which": if out { "out" } else { "in" }, "x": q.x, "y": q.y, "independent": true}),
                         )
                     }
+                    State::Reshape { id, seg, t, start, spine: true, .. } => Action::Preview(
+                        "object.blend.spine.reshapeSegment".into(),
+                        json!({"id": id.0, "segment": seg, "t": t, "dx": p.x - start.x, "dy": p.y - start.y}),
+                    ),
                     State::Reshape { id, si, seg, t, start, .. } => Action::Preview(
                         "path.reshapeSegment".into(),
                         json!({"id": id.0, "subpath": si, "segment": seg, "t": t, "dx": p.x - start.x, "dy": p.y - start.y}),

crates/ui-egui/src/i18n/de.tsv

@@ -1545,6 +1545,7 @@
 	Move Rows	Zeilen verschieben
 	Move Slices	Slices verschieben
 	Move Spine Point	Achsenpunkt verschieben
+	Reshape Spine Segment	Achsensegment umformen
 	Move Swatch	Farbfeld verschieben
 	Move Up	Nach oben verschieben
 	Move…	Verschieben…

crates/ui-egui/src/i18n/es.tsv

@@ -1563,6 +1563,7 @@
 	Move Rows	Mover filas
 	Move Slices	Mover sectores
 	Move Spine Point	Mover punto del eje
+	Reshape Spine Segment	Remodelar segmento del eje
 	Move Swatch	Mover muestra
 	Move Up	Subir
 	Move…	Mover…

crates/ui-egui/src/i18n/fr.tsv

@@ -1562,6 +1562,7 @@
 	Move Rows	Déplacer les lignes
 	Move Slices	Déplacer les tranches
 	Move Spine Point	Déplacer le point de la dorsale
+	Reshape Spine Segment	Modeler le segment de la dorsale
 	Move Swatch	Déplacer la nuance
 	Move Up	Monter
 	Move…	Déplacer…

crates/ui-egui/src/i18n/it.tsv

@@ -1563,6 +1563,7 @@
 	Move Rows	Sposta righe
 	Move Slices	Sposta sezioni
 	Move Spine Point	Sposta punto dorsale
+	Reshape Spine Segment	Rimodella segmento della dorsale
 	Move Swatch	Sposta campione
 	Move Up	Sposta su
 	Move…	Sposta…

crates/ui-egui/src/i18n/ja.tsv

@@ -1697,6 +1697,7 @@
 	Move Rows	行を移動
 	Move Slices	スライスを移動
 	Move Spine Point	スパインポイントを移動
+	Reshape Spine Segment	スパインセグメントをシェイプ変形
 	Move Swatch	スウォッチを移動
 	Move Up	上へ移動
 	Move in Perspective	遠近で移動

crates/ui-egui/src/i18n/pt-br.tsv

@@ -1334,6 +1334,7 @@
 	Move Plane to Match Object	Mover Plano para Corresponder ao Objeto
 	Move Slices	Mover Fatias
 	Move Spine Point	Mover Ponto de Coluna
+	Reshape Spine Segment	Remodelar Segmento da Coluna
 	Move Swatch	Mover Amostra
 	Move Up	Mover para Cima
 	Move in Perspective	Mover em Perspectiva

crates/ui-egui/src/i18n/ru.tsv

@@ -1561,6 +1561,7 @@
 	Move Rows	Переместить строки
 	Move Slices	Переместить фрагменты
 	Move Spine Point	Переместить точку остова
+	Reshape Spine Segment	Изменить форму сегмента остова
 	Move Swatch	Переместить образец
 	Move Up	Переместить вверх
 	Move…	Переместить…

crates/ui-egui/src/i18n/uk.tsv

@@ -1557,6 +1557,7 @@
 	Move Rows	Перемістити рядки
 	Move Slices	Перемістити фрагменти
 	Move Spine Point	Перемістити точку осі
+	Reshape Spine Segment	Змінити форму сегмента осі
 	Move Swatch	Перемістити зразок
 	Move Up	Перемістити вгору
 	Move…	Перемістити…

crates/ui-egui/src/i18n/zh-hans.tsv

@@ -1494,6 +1494,7 @@
 	Move Plane to Match Object	移动平面以符合对象
 	Move Slices	移动切片
 	Move Spine Point	移动脊线点
+	Reshape Spine Segment	整形脊线线段
 	Move Swatch	移动色板
 	Move Up	上移
 	Move…	移动…

crates/ui-egui/src/i18n/zh-hant.tsv

@@ -1538,6 +1538,7 @@
 	Move Rows	移動列
 	Move Slices	移動切片
 	Move Spine Point	移動脊線點
+	Reshape Spine Segment	改變脊線線段外框
 	Move Swatch	移動色票
 	Move Up	上移
 	Move…	移動…

docs/control-protocol.md

@@ -692,7 +692,9 @@ new blends start with. The Blend tool (`ui.tool.select {tool: "blend"}`): `ui.po
 another, blends them; down on an anchor point blends from that point; each further object clicked joins the blend.
 A selected blend shows its spine. With Direct Selection (`directSelection`) a `ui.pointer` drag from a spine point
 moves it (`object.blend.spine.moveAnchor`, one undo step) and, once a point is clicked, from one of its handles
-reshapes the curve; Direct and Group Selection pick a blend's key objects. With the Pen tool a click on a selected
+reshapes the curve, and a drag on a curved spine segment bends it (`object.blend.spine.reshapeSegment`); the Anchor
+Point tool (`anchorPoint`) bends any segment of a selected blend's spine, straight ones too. Direct and Group Selection
+pick a blend's key objects. With the Pen tool a click on a selected
 blend's spine adds a point (on a point no key sits on, deletes it).
 
 Perspective grid view options: View → Perspective Grid lists Show/Hide Grid, Show/Hide Rulers, Snap to Grid

docs/mcp.md

@@ -3077,8 +3077,9 @@ among the objects takes the others in as more key objects, keeping its options,
 A blend's spine is the straight lines between its key centres until it is edited. `object.blend.info` lists it
 (`spine.anchors`, `keyAnchors`: the point each key sits on). `object.blend.spine.addAnchor {x, y}` adds a point where
 the spine passes nearest, `object.blend.spine.moveAnchor {anchor, x, y}` moves a point (a key on it moves along; with
-`handle: "in" | "out"` it places that handle) and `object.blend.spine.removeAnchor {anchor}` deletes a point no key
-sits on; the first edit turns the spine into a path. Moving a key moves its end of the spine. Release
+`handle: "in" | "out"` it places that handle), `object.blend.spine.reshapeSegment {segment, t, dx, dy}` bends a segment
+so its point at `t` moves by (dx, dy), turning a straight spine into a curve, and `object.blend.spine.removeAnchor
+{anchor}` deletes a point no key sits on; the first edit turns the spine into a path. Moving a key moves its end of the spine. Release
 (`object.blend.release`) leaves the spine as a path that paints nothing (`spines` in the result):
 
 ```json